​As you can see the checkbox is on top of the label. I would like both to be "on the same line". So, it would look like "[ ] Accept the terms". And how would I make that the text is vertically aligned to the checkbox.

This is, however, somewhat fragile as the margins are a little arbitrary (and the margin-right is purely to force the following button to the next line). Also the attribute-equals selector may cause problems in older browsers.

As implied, in comments, by Mr. Alien it is actually easier to target the checkbox itself with this selector-notation: